1. Field of the Invention
This invention relates to an adjustable vehicle acceleration sensor useful in a seat belt winder (retractor).
2. Description of the Prior Art
In U.S. Pat. No. 4,039,158 to Weman, a winding device for a safety belt with a quick-acting lock is shown which has a pocket in a fastening mount and an inertial ball in the pocket. The pocket is open on one side, and when the vehicle is accelerated in one direction, the inertial ball moves out of the pocket and locks the winding shaft through a ratchet wheel.
For some time, there has been an increasing need to secure the belt winders not only on parts of the vehicle which are exactly horizontally or vertically arranged, but also on mounts arranged under an angle or on curved surfaces. If a mass produced belt winder is to be installed in different types of vehicles, it would be advisable to provide an adjustable belt winder, that is, a winder which can be installed under different angles, without having to utilize a separate belt winder for each mounting angle. In the above-mentioned known winding device, movable cylinders are therefore provided in the ring mount which can be turned with a screwdriver so that the belt winder can be adjusted to the corresponding mounting angle during the assembly.
On the other hand, there is a need for shortening the response time of the sensor device in the acceleration of the vehicle in one direction.
It has already been suggested in U.S. Pat. No. 4,176,809 to mount the inertial ball not in a pocket, as in the Weman patent, but on a trough with a sharp edge, hence on a ring facing to the inertial ball. Though the older suggestion, and also the present invention speaks substantially of an inertial ball, the latter can have a somewhat modified geometric form, provided it is rollable. Due to this suggestion with the relatively sharp edging on which the inertial ball is centered in its rest position, the manufacturing tolerances are no longer critical because the bearing surface of the inertial body on the respective ring is formed by its inner edge, which can even be oval. Without costly finishing of the support, a rapid response of the locking mechanism is thus ensured in an accident, and the inertial ball is also returned rapidly into its rest position. The uncertainty zone of the engagement between the pawl and ratchet wheel is thus kept very small. But the curved, preferably circular sharp edge on which the inertial ball is centered in its rest position is particularly functional only when the axis of the imaginary plane placed through the sharp ring edge is vertical. This, however, is responsible for the problem of adjustability to different angles.
In addition, the force necessary to displace the pawl by movement of the inertial ball is not uniform in all directions, but is somewhat increased in the direction of the major axis of the pawl. This is undesirable since it may result in too early an actuation in the other directions or too late an actuation in the said direction.
It would be desirable to provide a uniformly multidirection acceleration sensor for a seat belt retractor. It would also be desirable to provide a sensor device responding to vehicle acceleration adjustable in the above described manner, while maintaining the advantage of a rapidly achieved locking position and the rapid return of the inertial body, that is, the bearing on the ring.